The present invention is generally directed to a system, method, and apparatus for packaging electronic circuit components. More particularly, the present invention is directed to a system for electronic component packaging which permits easy insertion and removal of fully populated circuit boards without having to remove printed circuit cards which have already been inserted into the boards. Even more particularly, the present invention is directed to systems, methods, and devices which enhance the ability to package electronic components in a dense manner while still being able to provide not only air cooling but which also provides an effective system for electromagnetic interference (EMI) shielding.
It should be appreciated that not all of the features of the present invention need to be incorporated into a single device or system. Many of the features found in the present invention may be employed independently from one another. In general, the present invention seeks to solve a number of problems with respect to electronic circuit packaging. In particular, it is desirable to employ printed circuit cards which can be easily inserted and removed from printed circuit boards without the removal of the board and without removal of any cabinet or enclosure surrounding the electronics package. In desired embodiments of the present invention, therefore, it is found that printed circuit cards are capable of being xe2x80x9chot pluggedxe2x80x9d into a printed circuit board.
Additionally, it is noted that, in preferred embodiments of the present invention, circuit components operate at relatively high frequencies. At higher frequencies, problems associated with the propagation of electromagnetic interference become more significant. Accordingly, for those situations in which higher frequency components are desired, there is a correspondingly higher desire to employ electromagnetic shielding systems. Thus, there should be provided a mechanism for providing EMI shielding that is commensurate with the notions of hot pluggability. In other words, the EMI shielding system should be compatible with the notion that printed circuit cards are removed and inserted from printed circuit boards which are themselves not pluggable.
Hot pluggable systems are shown in U.S. Pat. No. 6,062,894 issued May 16, 2000, and assigned to the same assignee as the present invention. However, in the system described therein, there is a dependence on the existence of an external cabinet to effect the vertical motion of the printed circuit card into a corresponding mating socket on a printed circuit board. The presence of physical contact between the mechanism for insertion and removal and an enclosure which surrounds a printed circuit board precludes the use of such devices in mechanisms for which the entire printed circuit board itself is removable.
It is also noted that the present discussion refers to printed circuit boards and printed circuit cards. As contemplated herein, the printed circuit board is the larger component into which at least one printed circuit card is inserted for purposes of electrical connection. The present invention places no specific limits on either the size of a printed circuit board or the size of a printed circuit card. In the most general situation, a circuit board is populated with a plurality of printed circuit cards. That is, the printed board has a number of printed circuit cards inserted therein. Accordingly, as used herein, the terms xe2x80x9cprinted circuit boardxe2x80x9d and xe2x80x9cprinted circuit cardxe2x80x9d are considered to be relative terms. However, it is also noted that one of the motivating factors in the design of the present invention is the fact that printed circuit boards are, when fully populated, relatively heavy and possess one or more connectors at the edges thereof. These board edge connectors typically possess a large number of electrical connections to accommodate the correspondingly larger number of electrical connections that must be accommodated for a board which is populated with a number of printed circuit cards. The present inventors have also contemplated a mechanism for insertion of the entire board in a tight space without the necessity of removing any of the printed circuit cards. Accordingly, some of the specific situations contemplated by the present inventors have also resulted in the inclusion of mechanisms for insertion and removal of fully populated printed circuit boards.
Normally the circuit board, the mother board if you will, is considered fixed and does not usually constitute a movable structure. Moreover, even in those circumstances where one might contemplate inserting or removing a circuit board, one would normally not consider such an operation without first removing the printed circuit cards from the board. Because a typical printed circuit board is often populated with a relatively large number of printed circuit cards, the size and weight of the circuit board is typically relatively large. Thus, one is normally presented with the problem of moving (in forward and reverse directions) a large, flat, relatively thin substrate. Particularly during insertion operations, such a physical structure is likely to experience bending and flexing motions typically referred to as xe2x80x9coil canning.xe2x80x9d Accordingly, solutions to problems in the present art address this issue as well.
Accordingly, the present inventors are presented with the following sometimes competing packaging problems: oil canning, dense and close packaging, air cooling, electromagnetic interference shielding, hot pluggability, the desire to provide an easy to load cartridge for carrying printed circuit cards, mechanisms requiring a mechanical advantage for insertion and removal of entire circuit boards, the removal of fully populated boards and the insertion thereof, and means to provide a cooperative EMI shielding arrangement in a system which provides circuit board guide mechanisms which do not require physical contact with a surrounding enclosure or cabinet.
In accordance with a preferred embodiment of the present invention, a number of features are provided which together solve all of the competing problems indicated above. In particular, a significant aspect of the present invention is provision of a docking cartridge which serves as a printed circuit card carrier and which is capable, in and of itself, of inserting and removing electronic printed circuit cards. While the present invention is particularly suitable for the incorporation of printed circuit cards meeting the so-called PCI (Personal Computer Interface) Standard, the principles of the present invention are generally applicable to any printed circuit card having an edge connector which is insertable into a corresponding mating connector on a printed circuit board. The docking cartridge of the present invention includes an actuating mechanism for card insertion which is completely self contained and which does not rely upon any physical contact with an enclosure or cabinet. Rather, the docking cartridge of the present invention interacts with a single-sided cartridge guide mechanism which is provided at the printed circuit board level. Moreover, the docking cartridge of the present invention is provided with an easy load mechanism for the printed circuit card. In particular, the docking cartridge is provided with a front bezel which also constitutes part of an EMI shield mechanism and which is also pivotable with respect to a top cartridge wall structure. The top cartridge member is slidably disposed with respect to a circuit card carrier which contains corner clips and slidable adjustable mechanisms as shown in the aforementioned U.S. Pat. No. 6,062,894. The top member is thus slidably attached to a moveable carrier which moves the printed circuit board up and down so as to provide insertion and removal of the circuit board with respect to mating electrical connectors on the printed circuit board.
A front bezel of the docking cartridge is also provided with a mechanism for ensuring EMI shielding during the entire insertion and removal process. In particular, desirable circuit boards for use in connection with the present invention include a front EMI shield plate which has electrical contact with the front docking cartridge bezel. In particular, such desirable printed circuit cards having this plate also include, on the bottom of this shield plate, a tab portion which engages a flexible EMI shield strip which is disposed on an electrically conductive stiffener which provides protection against the aforementioned oil-canning effect and which furthermore provides its own degree of EMI shielding for board level circuits and components. The EMI shield strip used in the present invention possesses a geometric structure which renders it readily capable of being fabricated in stamping and forming operations. This EMI strip is disposed so that it includes slotted opening portions which engage edges of apertures found in parallel rows in the stiffener. The strip engages these apertures in one row and includes a flexible portion which extends into the opening in a parallel row of stiffener apertures. Thus, in accordance with the present invention, as the printed circuit is inserted into the printed circuit boards so as to make electrical contact with circuits on the board, there is also provided a continuous EMI shield as the tab on the printed circuit card engages a flexible tab portion on the EMI strip which is in electrical contact with the conductive stiffener.
One of the other significant problems addressed by the present invention is the fact that a fully populated circuit board is relatively heavy and typically possesses a large number of electrical circuit contacts thus increasing the force needed to provide proper electrical connection. The mechanism for providing this force should not be significantly large nor should it consume significant amounts of space. That is to say, the mechanism for inserting and removing the circuit board should be compact and consistent with the compact and dense packaging notions of the present invention. Furthermore, this mechanism should be compatible with the other structures provided herein, notably, the stiffener and the EMI shielding system.
The present invention incorporates two principle aspects. A first structural component utilizes an independent, self-contained cartridge for containing printed circuit cards intended for insertion into and removal from tight spaces. A second aspect of the present invention includes the structure of a printed circuit board which is usable in conjunction with the aforementioned cartridges. Furthermore, the cartridge and board system of the present invention cooperatively interact to provide EMI shielding mechanisms not only compatible with the easy insertion and removal of circuit cards, but which also provide a cooperative mechanism for the insertion and removal of an entire circuit board in its fully populated state, that is, with all printed circuit cards inserted and connected.
With respect to the first aspect of the present invention which relates to the cartridge for protecting, transporting, inserting, and the removal of printed circuit cards, it is noted that this cartridge includes three main components: a front bezel, a top cartridge wall member, and a movable carrier which is upwardly and downwardly movable with respect to the bezel and the top cartridge wall. The cartridge also includes a lever actuated mechanism attached to the top of the bezel which provides sufficient force for card insertion. The lever actuated mechanism of the cartridge is disposed in such a way as to provide both upward and downward forces to the movable carrier at a point along the carrier which is appropriate for both short and long printed circuit cards. The cartridge of the present invention also includes a side cover. In preferred embodiments of the present invention, the bezel is metal and is in continuous electrical contact with an EMI shield plate found on certain printed circuit cards which are desirably useful in conjunction with preferred embodiments of the present invention particularly when they operate at relatively high frequencies. These shield plates preferably include a lower tab portion which extends through an opening in the bottom of the front bezel and which engages an EMI shield spring which thus allows it to be electrically connected with a conductive stiffener affixed to the printed circuit board.
With respect to the second aspect of the present invention which relates to the printed circuit board itself, the board is provided with an electrically conductive shield and stiffener as mentioned above with respect to the incorporation of the tab and spring structures. Furthermore, printed circuit boards of the present invention include a nonconductive base member which is disposed on a side of the printed circuit board opposite the stiffener. This base support structure provides additional resistance to xe2x80x9coil canningxe2x80x9d effects that can occur particularly in larger printed circuit board structures. The printed circuit board also includes special guides disposed at the printed circuit board level. These guides engage ridges disposed on side wall covers for the printed circuit card cartridges, as described above. A particular feature of the cartridges also includes a mechanism for interlocking adjacent cartridges. Accordingly, a desirable aspect of the present invention is the fact that the special guides employed herein do not require slot and ridge structures to be present on both sides of the inserted cartridge. This is significant in the present invention since this feature permits cards to be made thinner and accordingly increases the overall packaging density which, as described above, is a highly desirable aspect of the present invention.
The stiffener employed in conjunction with the printed circuit board includes a front row of parallel slots which are spaced to receive an EMI spring shield structure which cooperates with the cartridge structure to provide a continuous EMI shield. Additionally, the present invention also includes a force-producing mechanism which is capable of providing a significant mechanical advantage for insertion and removal of the printed circuit board itself, even when requiring all of the board edge connectors to be mated with corresponding off-board connectors. In preferred embodiments of the present invention, the insertion and removal mechanism for the printed circuit board includes a toothed arm which engages a wrench-activated pinion gear which is affixed to the above-mentioned stiffener at the front or leading edge of the printed circuit board. The toothed arm is pivotally connected to force-producing arms which include pins which ride in slots in the base structure which supports the printed circuit board from below. As the pinion gear is rotated, the combination of the toothed arm and the force-providing levers changes to and from a xe2x80x9cTxe2x80x9d and xe2x80x9cYxe2x80x9d shape. Thus, as the pinion gear is rotated, the lever arms move in what is best described as a xe2x80x9cbackstrokexe2x80x9d motion. These levers push against cabinet or enclosure pins and, in doing so, cause the insertion or removal of the circuit board, in its entirety, into or out of a mating electrical connector.
The cartridge of the present invention is also constructed in such a manner so as to employ components which are pivotally connected so as to enable easy insertion of printed circuit cards having various dimensions. In effect, the maximum size of a card employed in the present invention is thus determined by the height of the bezel and the length of the cartridge top.
Accordingly, it is an object of the present invention to provide a system for packaging electronic circuit components in tight spaces.
It is also an object of the present invention to provide an apparatus for inserting and removing printed circuit cards in tight quarters.
It is a still further object of the present invention to provide a cartridge which is capable of transporting, protecting, inserting, and removing printed circuit cards in a self-contained manner.
It is also an object of the present invention to provide mechanisms which support hot pluggability of electronic circuit cards and boards.
It is a still further object of the present invention to provide a mechanism which permits insertion and removal of fully populated electronic circuit boards.
It is also an object of the present invention to provide a cartridge, for containing printed circuit cards, which is easily loadable.
It is furthermore an object of the present invention to provide a system in which continuous EMI shielding is provided between an easily removable printed circuit cartridge and a printed circuit board.
It is yet another object of the present invention to provide a cartridge for printed circuit cards which is readily adapted to hold cards of varying sizes.
It is yet another object of the present invention to provide a system of interlocked printed circuit card cartridges and a supporting printed circuit board.
It is yet another object of the present invention to provide a mechanism by which an entire fully populated printed circuit board is readily inserted into and removed from the system in which it is electrically connected.
It is also an object of the present invention to provide a printed circuit cartridge card carrying mechanism which is compatible with air cooling of the components contained on the card.
It is a still further object of the present invention to provide a printed circuit board which is still nonetheless compatible with the incorporation of ancillary circuit components such as capacitors, resistors, heat sinks, and the like which extend upward from the printed circuit board.
It is a yet another object of the present invention to provide an EMI shield spring structure which is operative as a mechanism for providing electrical connections and EMI shielding continuity between a printed circuit card and an EMI shield structure disposed on a printed circuit board to which the card is also separately electrically connected.
It is a further object of the present invention to provide a guide mechanism on a printed circuit board for cartridge insertion so as to consume only a small space in the side-to-side direction, between loaded cartridges.
Lastly, but not limited hereto, it is an object of the present invention to provide an integrated printed circuit card cartridge and printed circuit board mechanism which provide compactness, air-cooling capabilities, EMI shielding, hot pluggability, and mechanical force advantages both for the insertion and removal of printed circuit cards and the insertion and removal of fully populated printed circuit boards.
The recitation herein of a list of desirable objects which are met by various embodiments of the present invention is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present invention or in any of its more specific embodiments.